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FZJ-2020-00614

http://join2-wiki.gsi.de/foswiki/pub/Main/Artwork/join2_logo100x88.png Proteinkinase C-abhängige Phosphorylierung zyklisch-Nukleotid-gesteuerter Ionenkanäle aus den Sehzellen des Rindes

Vantler, M. (Corresponding author)FZJ*

2000
Forschungszentrum Jülich GmbH Zentralbibliothek, Verlag Jülich

Please use a persistent id in citations: http://hdl.handle.net/2128/24060

Report No.: Juel-3815

Abstract: In retinal rod and cone photoreceptor cells cyclic nucleotide-gated (CNG) channels mediatethe electrical response to stimulation by light. CNG channels are composed of differentsubunits, designated CNC$\alpha$ or CNC$\beta$ subunits. CNG channels are gated by the internalmessenger molecule cGMP and are modulated by small Ca$^{2+}$-binding proteins. This PhD-thesisshows that the CNG channels from rod and cone photoreceptor cells are phosphorylatedby protein kinase C (PKC). PKC-dependent phosphorylation of homomeric heterologouslyexpressed cone CNG channels composed of CNC$\alpha$2 subunits was investigatedelectrophysiologically in inside-out patches. Phosphorylation of two serine residues (serine577 and serine 579) in the cGMP-binding pocket of the CNC$\alpha$2 subunit decreases the ligandsensitivity of cone CNG channels by a factor of 2 - 3. The decrease in ligand sensitivity iscompletely abolished in mutant channels in which the two serine residues were replaced byalanine.The auxiliary CNC$\beta$1 a subunit of the rod CNG channel is phosphorylated by PKC too. The $\textit{invitro}$ phosphorylation of different recombinant fusion proteins shows that the phosphorylationsites are localized in the vicinity of the N-terminal calmodulin (CaM)-binding domain.Binding of CaM to the CNC$\beta$1a subunit reduces the degree of phosphorylation, whereasphosphorylation did not prevent CaM from binding.GARP2 is an N-terminal splice form of the CNC$\beta$1a subunit. In contrast to the CNC$\alpha$2 andCNC$\beta$1a subunit, GARP2 is not phosphorylated by PKC. Gel filtration experiments showedthat GARP2 binds the light-activated cGMP-hydrolyzing enzyme phosphodiesterase. In thisway GARP2 may organize an "adaptational" signaling complex at the disk rim of the rodphotoreceptor cell that controls cGMP turnover during daylight.

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Contributing Institute(s):

1. Publikationen vor 2000 (PRE-2000 ; Retrocat)

Research Program(s):

1. 899 - ohne Topic (POF3-899) (POF3-899)

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Database coverage:

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